Method for the production of polycondensates

ABSTRACT

A method for the production of polycondensates. The method is characterized in that waxes and polymer additives are used as lubricating and separating agents during the production of the polycondensate.

The invention relates to a process for preparing polycondensates.Plastics are usually processed in the melt. The associated changes instructure and state (e.g. crosslinking, oxidation, molecular weightchanges) cause some alteration in the chemical, physical, and technicalproperties of almost every plastic. To reduce the stress to whichplastics are exposed during their processing, various additives areused, among which are stabilizers, lubricants, antioxidants, releaseagents, dispersing agents, and others.

The sole use of various waxes as (mold-)release agents in plastics isknown in various plastics, in particular in polyamides. (Mold-)releaseagents often used are metal stearates, amide waxes, and montan waxesters.

Although the metal stearates improve the flowability of the melt, theyoften cause considerable molecular-weight degradation of the polymers.Montan wax esters and their salts improve the flowability of plastics,such as polyamides, solely through internal lubricant action, withoutreducing the molecular weight of the polymer.

Coloring, especially of polyamide, is rendered particularly difficult bythe high processing temperatures, and also by the chemically aggressivenature of the melt toward colorants, and there is a very restrictedchoice of colorants (pigments) and dispersing agents which may be used.Pigments often sustain lasting degradation due to the high addedshear-energy levels present during the dispersion process. Thedispersing agents, too, have to be optimized.

Montan waxes or amide waxes have previously been used as dispersingagents for pigments.

In principle, it is also possible to stabilize plastics in a downstreamprocess, but the homogenization achieved is often insufficient,especially if a pulverulent stabilizer is added to the plastics pellets.

Among the materials which have proven successful for stabilizing manyplastics, in particular polyamides, with respect to air, light, and heatare copper salts, aromatic amines, and sterically hindered phenols.

The abovementioned auxiliaries or agents may be introduced into theplastic at a very wide variety of steps in the process, for example atthe end of the polycondensation, or in a subsequent compounding process.It is also possible to apply pulverulent waxes to the (warm) plasticspellets in a drum mixer.

The prior-art action of the various agents and auxiliaries in plasticspreparation, in particular preparation of polycondensates, listedremains inadequate with respect to a number of properties, such asinternal and external lubricant action, and also dispersion of pigmentsand fillers, and the gloss of the plastic.

It was therefore an object of the present invention to provideauxiliaries or agents which have improved overall action on the plastic,in particular in the case of polyamides, in plastics preparation, inparticular preparation of polycondensates.

This object is achieved by way of a process of the type mentioned at theoutset, which comprises using waxes and polymer additives as lubricantsand release agents, and as dispersing agents, during the preparation ofthe polycondensate.

Surprisingly, it has been found that, when comparison is made with theuse of the individual substances, and also with a number of other waxes,the synergistic effects of waxes and polymer additives gives the bestresults, in particular in polyamides, in relation to internal andexternal lubricant action, and also dispersion of pigments and fillers,and gloss, in the process for preparing polycondensates.

A preferred wax is an ester wax and/or a salt of a carboxylic acid.

Another preferred wax is products of the reaction of montan wax acidswith ethylene glycol.

The products of the reaction are preferably a mixture of the mono(montanwax acid) ester of ethylene glycol, the di(montan wax acid) ester ofethylene glycol, montan wax acids, and ethylene glycol. Anotherpreferred wax is products of the reaction of montan wax acids with acalcium salt.

The products of the reaction are particularly preferably a mixture ofthe mono(montan wax acid) ester of 1,3-butanediol, the di(montan waxacid) ester of 1,3-butanediol, montan wax acids, 1,3-butanediol, calciummontanate, and the calcium salt.

A preferred polymer additive is a derivative of an aromatic di- ortricarboxylic (ester) amide.

A preferred derivative is N,N′-bispiperidyl-1,3-benzenedicarboxamide.

Another preferred derivative isN,N′-bis(2,2,6,6-tetramethyl-4-piperidyl)-1 ,3-benzenedicarboxamide.

A preferred ratio in which wax and polymer additive are used in theinventive process is from 1:9 to 9:1 by weight.

Another preferred ratio in which wax and polymer additive are used inthe inventive process is from 3:7 to 7:3 by weight.

Another preferred ratio in which wax and polymer additive are used inthe inventive process is from 4.5:5.5 to 5.5:4.5 by weight.

The polycondensate is preferably polyamide.

The polyamides are preferably of amino-acid type and/or ofdiamine-dicarboxylic-acid type.

The polyamides are preferably nylon-6 and/or nylon-6,6.

The polyamides are preferably unmodified, colored, filled, unfilled,reinforced, or unreinforced polyamides, or else polyamides which havebeen otherwise modified.

It is preferable to use wax and polymer additive in the form of pellets,flakes, fine grains, powder, and/or micronizate.

Wax and polymer additive are preferably introduced in the same ordifferent steps of the process during the preparation/processing ofpolyamides.

Wax and polymer additive are preferably incorporated duringpolycondensation, during the compounding process, or directly during theshaping process.

It is preferable to use wax and polymer additive individually, in theform of a physical mixture of the solids, in the form of a melt mixture,in the form of a compactate, or in the form of a masterbatch.

The total amount used of wax and polymer additive is preferably from0.01 to 10.00% by weight, based on the polyamide.

The total amount used of wax and polymer additive is particularlypreferably from 0.1 to 2.00% by weight, based on the polyamide.

Suitable lubricants for the inventive process are montan waxes, whichmay be described as a mixture of a long-chain linear saturatedcarboxylic acid having from 24 to 36 carbon atoms with various esters ofthis carboxylic acid with different alcohols, and with the salts of thecarboxylic acids. They often comprise native montan wax, i.e. the esterof a. long-chain carboxylic acid with a long-chain monohydric alcohol.

Use is also made of esters of montan wax acid with glycol, glycerol,butanediol (1,3- and 1,4-), trimethylolpropane, pentaerythritol, anddipentaerythritol, and partially hydrolyzed products of these. Thehydrolysis number of these products may be varied, as may their acidnumber and, where appropriate, their metal content.

Preferred montan waxes which may be used for the inventive process areproducts of the reaction of montan wax acid or, respectively, a mixtureof native montan wax esters and of montan wax acids, with ethyleneglycol to give a mixture of the mono- and diester and of the startingmaterials (e.g. ®Licowax E, Clariant GmbH). The calcium salt of themontan wax acids is also particularly suitable. This product is aproduct of the reaction of montan wax acid or, respectively, a mixtureof native montan wax esters and of montan wax acids, with a calcium saltto give a mixture of calcium montanate and the starting materials (e.g.®Licomont CaV 102, Clariant GmbH).

Preferred polymer additives which may be used for the inventive processcomprise compounds of the type represented by the aromatic di- ortricarboxylic esters or aromatic di- or tricarboxamides. In particular,it has been found that substituted substances of the type represented byN,N′-bispiperidyl-1,3-benzenedicarboxamide, such asN,N′-bis(2,2,6,6-tetramethyl4-piperidyl)-1,3-benzenedicarboxamide(Nylostab® S-EED, Clariant GmbH) are suitable.

When the inventive process for polycondensates (polyamides) uses waxesand polymer additives, the level of internal and external lubricantaction is increased, and the flowability is improved. Another result isvery powerful release action and a marked reduction in the tendency ofthe polyamide molding composition to adhere to hot components ofmachines.

The use of wax and polymer additive according to the present inventionalso markedly improves the optical properties of a polyamide molding(surface gloss).

In the inventive process for preparing polycondensates in pigmentmasterbatches using polyamide as carrier material, the use of wax andpolymer additive improves properties, in particular those concerned withfiner and more uniform distribution of pigments and fillers, this beingdiscernable through a markedly lower filter pressure Value, and alsothrough increased color strength.

The inventive process for preparing polycondensates incorporatespulverulent or fine-grain substances via mixing or adsorption of theseonto the cold or warm carrier polymer, and then processing through amolding step (e.g. injection molding, flat-film production,calendering), or, respectively, through prior compounding by means of anextruder, where wax or, respectively, polymer additive may be metered bymeans of lateral feed, or may be previously incorporated by mixing intothe polyamide.

EXAMPLES

The release action (external lubricant action) of lubricants inengineering plastics, such as polyamide, is quantified via measurementof demolding force during injection molding. For this, the cylindricalshell is produced by the injection-molding process, and the demoldingforce recorded is the maximum force needed to demold the shell from themold. The lower the demolding force, the better the external lubricantaction of the lubricant used.

The studies used a specific grade of nylon-6 in which no lubricants ofany kind are present, the result being that this grade cannot beprocessed until lubricants have been added. The demolding force is >10000 N. The lubricants and additives were incorporated by mixing into thepolymer pellet, and by means of compounding in a twin-screw extruder,followed, after predrying, by injection molding.

All of the experiments were carried out under identical conditions(temperature programs, screw geometries, injection-molding parameters,etc.) for reasons of comparability.

Example 1 (Release Action (External Lubricant Action))

Nylon-6, unreinforced 0.15 phr of Nylostab S-EED* + 0.15 phr calcium    400 N montanate Comparison: Nylon-6 without lubricant >10 000 N 0.3phr Nylostab S-EED*    1 500 N 0.3 phr calcium montanate     550 N 0.3phr montan wax ester     550 N(*Nylostab S-EED isN,N-bis(2,2,6,6-tetramethyl-4-piperidyl)-1,3-benzenedicarboxamide)

Nylon-6, glass-fiber-reinforced 0.15 phr Nylostab S-EED + 0.15 phrcalcium montanate  850 N 0.15 phr Nylostab S-EED + 0.15 phr montan waxester  800 N Comparison: Nylon-6 (30% glass fiber) without lubricant 2500 N 0.3 phr calcium montanate 1 000 N 0.3 phr montan wax ester  900 N

The improvement in flow (internal lubricant action) provided bylubricants in engineering plastics, such as polyamide, is usuallyquantified by determining the flow distance by means of a “spiral test”.For this, a graduated spiral is produced by the injection-moldingprocess, and its length is determined. The longer the flow path (i.e.the spiral), the better the internal lubricant action, i.e. theflowability of the polymer.

Operations were carried out as in example 1, and use was made of thespecific polyamide of example 1.

Example 2 (Flow Improvement in Polyamide (Internal Lubricant Action))

0.15 phr Nylostab S-EED + 0.15 phr calcium montanate 42.0 cm Comparison:0.3 phr Nylostab S-EED 40.5 cm 0.3 phr calcium montanate 41.0 cm

This flow improvement could not be achieved by any of the lubricantsknown from the prior art.

Gloss determination uses a reflectometer in which the reflected light ismeasured for a particular angle of incidence (reflection angle).According to DIN 67530, surfaces which, as in the present case, exhibitValues above 70 units at a 60° reflection angle are to be tested at areflection angle of 200. The following Values were obtained onmeasurement at a reflection angle of 20°: the injection-molded plaquesfor the gloss measurement were produced under constant conditions, forreasons of comparability.

Example 3 Gloss of Compounded Polyamide Materials

0.15 phr Nylostab S-EED/0.15 phr calcium montanate 89 gloss unitsComparison: Nylon-6 without lubricant 87 gloss units 0.3 phr NylostabS-EED 65 gloss units 0.3 phr calcium montanate 70 gloss units

Specifically in the case of masterbatches using engineering plastics,such as polyamide, montan waxes are used as dispersing agents to wet thepigments, in order to comminute the pigments, which tend to agglomerateand are difficult to disperse. This effect is quantified by way of whatis known as the filter pressure test, in which the pressure increaseupstream of a filter of particular mesh width is measured, the increasebeing greater as the size of the agglomerates increases with the resultthat they block the filter. Pigments which have been better dispersedhave better capability to pass through the filter, and dispersionquality is higher. A small filter-pressure value measured in [bar/g ofpigment] is therefore a measure of good dispersing action of thelubricants.

PV Fast Pink was chosen as pigment, because it has low dispersibility inpolyamide. Additive-free nylon-6 was used as carrier, and it wastherefore possible to study the isolated action of the additives added.Surprisingly, it was found here that the inventive combinations composedof wax (montan waxes, such as montan wax esters or calcium montanate)and a polymer additive (® Nylostab S-EED) give extremely gooddispersion,.i.e. give low filter-pressure Values, this dispersion notbeing achievable through any other combination.

The pigments and additives were incorporated by means of cold mixing andby compounding in a twin-screw extruder. The pressure-filter Value wasthen determined by way of a 14 μm filter.

Example 4 Dispersion of Pigments in Polyamides

Unreinforced 60% 60% 60% 65% 65% 65% 65% 65% nylon-6 PV Fast Pink E 30%30% 30% 30% 30% 30% 30% 30% Nylostab  5%  5% S-EED Calcium  5% 10%montanate Montan wax  5%  5% ester Licowax OP  5% Licolub WE 40  5%Licolub WE 4  5% Ceridust ®  5% 5551 Filter-pressure 4.0 3.6 18.0 6.011.4 13.4 12.0 16.6 value [bar/g of pigment]

1. A process for preparing polycondensate comprising the step of addingat least one wax and at least one polymer additive during thepreparation of the polycondensate, wherein the at least one wax and atleast one polymer additive act as lubricants release agents ordispersing agents, and wherein the at least one wax is the products ofthe reaction of montan wax acids with ethylene glycol, or the productsof the reaction of montan wax acids with a calcium salt, and the atleast one polymer additive is a derivative of an aromatic di- ortricarboxylic (ester) amide.
 2. The process as claimed in claim 1,wherein the products of the reaction of montan wax acids with ethyleneglycol are a mixture of the mono(montan wax acid) ester of ethyleneglycol, the di(montan wax acid) ester of ethylene glycol, montan waxacids, and ethylene glycol.
 3. The process as claimed in claim 1,wherein the products of the reaction of montan wax acids with a calciumsalt are a mixture of the mono(montan wax acid) ester of 1,3-butanediol,the di(montan wax acid) ester of 1,3-butanediol, montan wax acids,1,3-butanediol, calcium montanate, and the calcium salt.
 4. The processas claimed in claim 1, wherein the derivative of an aromatic di- ortricarboxylic (ester) amide is selected from the group consisting ofN,N′-bispiperidyl-1,3-benzenedicarboxamideN,N′-bis(2,2,6,6-tetramethyl-4-piperidyl)-1,3-benzenedicarboxamide andmixtures thereof.
 5. The process as claimed in claim 1, wherein the atleast one wax and the at least one polymer additive are present in aratio by weight of from 1:9 to 9:1.
 6. The process as claimed in claim1, wherein the at least one wax and the at least one polymer additiveare present in a ratio by weight of from 3:7 to 7:3.
 7. The process asclaimed in claim 1, wherein the at least one wax and the at least onepolymer additive are present in a ratio by weight of from 4.5:5.5 to5.5:4.5.
 8. The process as claimed in claim 1, wherein thepolycondensate is polyamide.
 9. The process as claimed in claim 8,wherein the polyamide is selected from the group consisting of theamino-acid type, the diamine-dicarboxylic-acid type and mixturesthereof.
 10. The process as claimed in claim 8, wherein the polyamide isselected from the group consisting of nylon-6, nylon-6,6 and mixturesthereof.
 11. The process as claimed in claim 8, wherein the polyamide isselected from the group consisting of unmodified, modified, colored,filled, unfilled, reinforced, or unreinforced polyamides.
 12. Theprocess as claimed in claim 1, wherein the at least one wax and the atleast one polymer additive in the form selected from the groupconsisting of pellets, flakes, fine grains, powder, micronizate andmixtures thereof.
 13. (Cancelled)
 14. (Cancelled)
 15. The process asclaimed in claim 1, wherein the at least one wax and the at least onepolymer additive individually, are in the form selected from the groupconsisting of a physical mixture solids, a melt mixture, a compactate,and a masterbatch.
 16. The process as claimed in claim 1, wherein the atleast one wax and the at least one polymer additive are present in anamount from 0.01 to 10.00% by weight, based on the polycondensate. 17.The process as claimed in claim 1, wherein the at least one wax and theat least one polymer additive are present in an amount from 0.1 to 2.00%by weight, based on the polycondensate.
 18. A polycondensate made inaccordance with the process of claim
 1. 19. A process for producing apolycondensate comprising the steps of: polycondensing at least twocompounds to form a polycondensate; compounding the polycondensate;shaping the polycondensate; adding, in a first adding step, at least onewax, wherein the at least one wax is the products of the reaction ofmontan wax acids with ethylene glycol, or the products of the reactionof montan wax acids with a calcium salt; adding, in a second addingstep, at least one polymer additive, wherein the at least one polymeradditive is a derivative of an aromatic di- or tricarboxylic (ester)amide; and wherein the first adding step, and the second adding step,individually, are performed during the polycondensing, compounding,and/or shaping step.